Pump for brake system

ABSTRACT

A pump for a brake system for increasing sealing performance between a piston and a bore as well as motion performance and durability of the piston and facilitating assembling efficiency of the piston. The pump includes a bore formed in a modulator block and connected to a suction port and discharge port, a piston installed in the bore to perform rectilinear reciprocating motions and having an oil flow path to move oil suctioned through the suction port toward the discharge port, an inlet valve to open and close the oil flow path in accordance with the motions of the piston, an outlet valve to selectively allow the discharge of compressed oil, and a fixing unit having a guide member provided around the piston to be coupled to the bore and adapted to guide the motions of the piston and a sealing member provided around the piston to be coupled to the bore and adapted to keep the bore and the piston in an air-tightness state.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2005-0112256, filed on Nov. 23, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump for a brake system, and, more particularly, to a pump for a brake system for achieving an improvement in oil pumping performance and pump assembling efficiency.

2. Description of the Related Art

Generally, a brake system has the purpose of efficiently preventing a wheel slip caused upon braking, quick start, or sudden acceleration of a vehicle. The brake system includes a plurality of solenoid valves to control a braking hydraulic pressure to be transmitted to hydraulic brakes of vehicle wheels, a pair of low-pressure and high-pressure accumulators to temporarily store an oil discharged from the hydraulic brakes, a pair of pumps provided between the low-pressure and high-pressure accumulators, the pumps being operated by a motor, and an ECU to control operations of the solenoid valves and motor. All the above elements are received in a modulator block made of aluminum.

In particular, the pumps of the brake system serve to forcibly pump the oil stored in the low-pressure accumulator or master cylinder to the high-pressure accumulator, so as to transfer the oil to the hydraulic brakes or master cylinder.

Many patents, including Korean Patent Laid-open No. 10-2005-0050168 and Korean Patent Registration No. 10-0381592 filed by the applicant of the present invention, disclose conventional pumps for a conventional electronically controlled brake system.

Explaining the conventional electronically controlled brake system in brief, it includes a booster and master cylinder associated with a brake pedal, a plurality of solenoid valves to control a braking hydraulic pressure to be transmitted to hydraulic brakes installed at front and rear vehicle wheels, a low-pressure accumulator to temporarily store oil discharged from the hydraulic brakes, a pair of pumps to pump the oil in the low-pressure accumulator or master cylinder, a motor to drive the pair of pumps simultaneously, and a high-pressure accumulator having an orifice disposed at an exit side thereof to reduce a pressure pulsation of the oil compressed and discharged by operation of the pumps. All the above elements are received in a modulator block made of aluminum. The pair of pumps are operated by the single motor to have a predetermined phase difference, thereby compressing the oil in the low-pressure accumulator or master cylinder and pumping the compressed oil to the high-pressure accumulator. Herein, further detailed description of the brake system will be omitted because it is fully disclosed in the above mentioned patent documents related to the prior art.

FIG. 1 illustrates a conventional pump for a brake system. The conventional brake system comprises a motor 10, a spindle 11 to be rotated by the motor 10, an eccentric shaft 12 to be eccentrically rotated by the spindle 11, a bearing 13 installed around the eccentric shaft 12, a piston 30 installed in a bore 21 formed in a modulator block 20 to perform reciprocating motions under the assistance of the bearing 13, the piston 30 having an inner oil flow path 31, an inlet valve 40 to open and close an exit side of the oil flow path 31 based on a position of the piston 30, and an outlet valve 60 provided at an open end of the bore 21, operations of the inlet and outlet valves 40 and 60 being contrary to each other.

The modulator block 20 is formed with a suction port 22 and a discharge port 23. The suction port 22 is used to connect an entrance side of the oil flow path 31 defined in the piston 30 to a low-pressure accumulator (not shown) or master cylinder (not shown), and the discharge port 23 is used to connect the an entrance side of a high-pressure accumulator (not shown) to an exit side of the outlet valve 60. The discharge port 23 communicates with the bore 21.

The inlet valve 40 for opening and closing the oil flow path 31 includes a valve opening/closing member 42 installed at an exit-side end of the oil flow path 31, a valve spring 43 to elastically push the valve opening/closing member 42 toward the exit side of the oil flow path 31, and a holder 44 configured to receive the valve opening/closing member 42 and valve spring 43. Also, a conical valve seat 41 is formed at an end of the piston 30 in the exit side of the oil flow path 31. The valve seat 41 is adapted to come into contact with or be spaced apart from the valve opening/closing member 42.

A valve cover 50 is also installed in the bore 21. The piston 30 assembled, at one end thereof, with the inlet valve 40 is inserted in the valve cover 50. The outlet valve 60 is also inserted in the valve cover 50. The valve cover 50 defines a compression chamber 51 with the end of the piston 30 in accordance with the reciprocating motions of the piston 30.

In the conventional pump having the above described configuration, if the motor 10 operates, the spindle 11 is rotated and thus, the eccentric shaft 12 is eccentrically rotated, causing rectilinear reciprocating motions of the piston 30. Thereby, as the inlet and outlet valves 40 and 60 perform opening and closing operations contrary to each other by a pressure variation in the bore 21, oil is compressed and pumped to the high-pressure accumulator (not-shown).

Specifically, if the piston 30 moves toward the outlet valve 60, a pressure of the oil between the piston 30 and the outlet valve 60 rises, causing the inlet valve 40 to be closed and the outlet valve 60 to be opened. Thereby, the oil is pumped to the high-pressure accumulator (not shown) through the discharge port 23.

On the other hand, if the piston 30 moves toward the bearing 13, the pressure of the oil between the end of the piston 30 and the outlet valve 60 falls, causing the inlet valve 40 to be opened and the outlet valve 60 to be closed. Thereby, the oil stored in the low-pressure accumulator (not shown) or master cylinder (not shown) is suctioned into a space between the piston 30 and the outlet valve 60, i.e. compression chamber 51, through the suction port 22 and oil flow path 31.

In addition to the above described configuration, seal members 32 are provided to prevent any possible leakage of the oil from a gap between the piston 30 and the bore 21 during operation of the piston 30.

However, the above described conventional brake system has many problems as follows. Firstly, since the bore 21 guides the reciprocating motions of the piston 30 and the seal members 32 move together with the piston 30, there is a problem in that the piston and bore may cause a gap therebetween due to their friction contact, and the gap may result in serious deterioration in sealing performance by the seal members. Secondly, the seal members have a limit in sealing effect because they are secured to the piston and adapted to move together with the piston. Thirdly, the conventional brake system suffers from low durability thereof due to wear of an inner portion of the bore, an outer portion of the piston, seal members, etc. Fourthly, the piston may be easily separated from the bore in a state wherein the motor, spindle, eccentric shaft, bearing, etc. are removed from the modulator block for the assembling or disassembling of the pump, and reassembling the piston into the bore is a very difficult and troublesome work.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve the above problems. It is an aspect of the invention to provide a pump for a brake system which can achieve an increase in sealing performance between a piston and a bore as well as motion performance and durability of the piston, and can guarantee easy assembling of the piston into the bore.

Consistent with one aspect, an exemplary embodiment of the present invention provides a pump for a brake system comprising: a bore formed in a modulator block and connected to a suction port and discharge port; a piston installed in the bore to perform rectilinear reciprocating motions, the piston comprising an oil flow path to move an oil suctioned through the suction port toward the discharge port; an inlet valve to open and close the oil flow path in accordance with the motions of the piston and an outlet valve to selectively allow the discharge of the compressed oil; and a fixing unit comprising a guide member provided around the piston to be coupled to the bore and adapted to guide the motions of the piston and a sealing member provided around the piston to be coupled to the bore and adapted to keep between the bore and the piston in an air-tightness state.

The guide member and sealing member may be integrally formed with each other to constitute the fixing unit.

The piston may have a protruding portion to be caught by the fixing unit, so as to prevent the piston from extending out of the bore beyond a predetermined length.

The inlet valve may comprise a valve seat formed at an end of the oil flow path, a valve opening/closing member to open and close the valve seat, a valve spring to elastically support the valve opening/closing member, and a holder to hold the valve spring at a fixed position, the holder having an end configured to be caught by the fixing unit, so as to prevent the piston from extending out of the bore beyond a predetermined length.

The pump may further comprise: a guide bush provided between the piston and the bore to guide the motions of the piston; and a sliding seal member adapted to slide between the guide bush and the fixing unit so as to keep between the piston and the bore in an air-tightness state, and the fixing unit may be extended from the inlet valve of the piston and adapted to support the sliding seal member to thereby prevent the sliding seal member from sliding beyond a predetermined distance.

The pump may further comprise: a valve seat coupled to the piston, the valve seat defining an exit of the oil flow path to be opened and closed by the inlet valve, and the valve seat may have a protruding portion to be caught by the fixing unit, so as to prevent the piston from extending out of the bore beyond a predetermined length.

The piston may have a stepped portion defined between different outer-diameter portions thereof, and the fixing unit has a holding portion defined between different inner-diameter portions thereof, the stepped portion being caught by the holding portion to prevent the piston from extending out of the bore beyond a predetermined length.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the exemplary embodiments of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:

FIG. 1 is a sectional view showing a conventional pump for a brake system;

FIG. 2 is a sectional view showing a pump for a brake system consistent with a first embodiment of the present invention;

FIG. 3 is a sectional view showing a pump for a brake system consistent with a third embodiment of the present invention;

FIG. 4 is a sectional view showing a pump for a brake system consistent with a fifth embodiment of the present invention; and

FIG. 5 is a sectional view showing a pump for a brake system consistent with a seventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain a pump for a brake system consistent with the present invention by referring to the figures.

First Embodiment

FIG. 2 is a sectional view showing a pump for a brake system consistent with a first embodiment of the present invention.

As shown in FIG. 2, the pump for a brake system consistent with the present invention comprises a motor 100, a spindle 110, an eccentric shaft 120 and a bearing 130, which are installed in a modulator block 200. A bore 210 is formed in the modulator block 200, and a piston 300 is inserted in the bore 210 to perform rectilinear reciprocating motions using a force transmitted from the bearing 130. The modulator block 200 is also formed with a suction port 211 and a discharge port 212. If oil from a low-pressure accumulator (not shown) or master cylinder (not shown) is introduced into the pump through the suction port 211, the oil is compressed in the pump and discharged to a high-pressure accumulator (not shown) through the discharge port 212.

A fixing unit 400 is located between an inner circumference of the bore 210 and an outer circumference of the piston 300 and coupled to the bore 210. The fixing unit 400 includes a guide member 401 to guide the rectilinear reciprocating motions of the piston 300 and a sealing member 402 to seal a gap between the bore 210 and piston 300 in an air-tightness state, so as to eliminate the risk of oil leakage.

The piston 300 has an oil flow path 310 formed therein for the movement of the oil suctioned from the suction port 211. A valve seat member 560 is installed at an exit side of the oil flow path 310, i.e. at a leading end of the piston 300, and in turn, an inlet valve 500 is installed at a leading end of the valve seat member 560. The inlet valve 500 is adapted to open and close the oil flow path 310 for controlling introduction or discharge of the oil into or from the oil flow path 310.

The inlet valve 500 includes a valve seat 510 formed at the leading end of the valve seat member 560, a valve opening/closing member 520 to come into contact with or be spaced apart from the valve seat 510, a valve spring 530 to elastically support the valve opening/closing member 520, and a holder 540 configured to receive and support all the above elements.

The inlet valve 500 installed at the leading end of the piston 300 defines a compression chamber 610 with a valve cover 600 fixedly installed in the bore 210. Both the valve seat member 560 and holder 540 formed at the leading end of the piston 300 are elastically supported by a return spring 550 crossing the compression chamber 610. Thereby, when the piston 300 is moved forward to compress the oil, the piston 300 is able to be moved rearward by the return spring 550.

An outlet valve 700 is installed in the valve cover 600 and adapted to control the discharge of the oil compressed in the compression chamber 610. The outlet valve 700 includes an outlet valve seat 710 defining an orifice 620 for the movement of the compressed oil, an outlet valve opening/closing member 720 to open and close the outlet valve seat 710, and a valve spring 730 to elastically support the outlet valve opening/closing member 720.

To prevent the piston 300 from extending out of the bore 210 beyond a predetermined length, the valve seat member 560 has a protruding portion 561 to be caught by the fixing unit 400.

Independently of the fixing unit 400, the piston 300 is externally provided with a guide bush 420 and a sliding seal member 410. The guide bush 420 is coupled to the bore 210 at a trailing end of the piston 300 and adapted to guide the reciprocating motions of the piston 300. The sliding seal member 410 is slidable between the guide bush 420 and the fixing unit 400, to seal a gap between the piston 300 and the bore 210.

The fixing unit 400 is extended by a predetermined length to limit a movement range of the sliding seal member 410. Consequently, the fixing unit 400 has the function of preventing excessive sliding movement of the sliding seal member 410.

Herein, a series of courses for introducing the oil into the suction port 211 and discharging the oil from the discharge port 212 will not be described because they are similar to the prior art.

Second Embodiment

Although a pump for a brake system consistent with a second embodiment of the present invention is not shown in the drawing, it is noted that the present embodiment is similar to the above described first embodiment except for the fact that the guide member 401 and sealing member 402 of the fixing unit 400 are integrally formed with each other.

Specifically, in the second embodiment of the present invention, the guide member 401 and sealing member 402 are made of the same elastic material as each other to form the single fixing unit 400, so as to perform both piston guiding and sealing functions together.

Third Embodiment

FIG. 3 is a sectional view showing a pump for a brake system consistent with a third embodiment of the present invention.

As shown in FIG. 3, the pump of the present embodiment is basically the same as that of the above described first embodiment in several ways, such as, the piston 300 is arranged to perform the rectilinear reciprocating motions in the bore 210 formed in the modulator block 200, the guide member 401 and sealing member 402 are provided between the inner circumference of the bore 210 and the outer circumference of the piston 300, and the like.

However, the third embodiment of the present invention as shown in FIG. 3 has a feature in that the valve seat 510 is formed by processing the piston 300, instead of installing the valve seat member 560 at the leading end of the piston 300 as described in relation with the first embodiment of the present invention, and a stopper 301 is formed around the valve seat 510. The stopper 301 is configured to be caught by the fixing unit 400, and serves to prevent the piston 300 from extending out of the bore 210 beyond a predetermined length. The stopper 310 has the effect of facilitating the assembling or disassembling of the piston 300 into or from the bore 210 formed in the modulator block 200.

The function and operation of other elements shown in FIG. 3 are the same as those of the above described first embodiment of the present invention shown in FIG. 2.

Fourth Embodiment

Although a pump for a brake system consistent with a fourth embodiment of the present invention is not shown in the drawing, it is noted that the present embodiment is similar to the above described third embodiment except for the fact that the guide member 401 and sealing member 402 of the fixing unit 400 are integrally formed with each other.

Specifically, in the fourth embodiment of the present invention, the guide member 401 and sealing member 402 are made of the same elastic material as each other to form the single fixing unit 400, so as to perform both piston guiding and sealing functions together.

Fifth Embodiment

FIG. 4 is a sectional view showing a pump for a brake system consistent with a fifth embodiment of the present invention.

As shown in FIG. 4, the pump of the present embodiment is basically the same as that of the above described third embodiment in several ways, such as, the piston 300 performs the rectilinear reciprocating motions in the bore 210 formed in the modulator block 200, the guide member 401 and sealing member 402 are provided between the inner circumference of the bore 210 and the outer circumference of the piston 300, and the like.

However, the fifth embodiment of the present invention as shown in FIG. 4 has a feature in that, instead of forming a stopper at the piston, an end portion of the holder 540 is bent outward to form a flange portion 541. Thereby, as the flange portion 541 is caught by the fixing unit 400, it is possible to prevent the piston 300 from extending out of the bore 210 by a predetermined length, and this enables easy assembling of the piston 300.

The function and operation of other elements shown in FIG. 4 are the same as those of the above described third embodiment of the present invention shown in FIG. 3.

Sixth Embodiment

Although a pump for a brake system consistent with a sixth embodiment of the present invention is not shown in the drawing, it is noted that the present embodiment is similar to the above described fifth embodiment except for the fact that the guide member 401 and sealing member 402 of the fixing unit 400 are integrally formed with each other.

Specifically, in the sixth embodiment of the present invention, the guide member 401 and sealing member 402 are made of the same elastic material as each other to form the single fixing unit 400, so as to perform both piston guiding and sealing functions together.

Seventh Embodiment

FIG. 5 is a sectional view showing a pump for a brake system consistent with a seventh embodiment of the present invention.

As shown in FIG. 5, the pump of the present embodiment is basically the same as that of the above described fifth embodiment in several ways, such as, the piston 300 performs the rectilinear reciprocating motions in the bore 210 formed in the modulator block 200, the guide member 401 and sealing member 402 are provided between the inner circumference of the bore 210 and the outer circumference of the piston 300, and the like.

However, the seventh embodiment of the present invention as shown in FIG. 5 has a feature in that the piston 300 is provided with a stepped portion 302, rather than providing the holder with the flange portion. Specifically, the piston 300 consists of two parts having different outer-diameters from each other, and thus, the stepped portion 302 is formed between the large-diameter part and the small-diameter part. Also, the fixing unit 400 consists of two parts having different inner-diameters from each other, and thus, a stepped holding portion 403 is formed between the small-diameter part and the large-diameter part. With this configuration, the stepped portion 302 is caught by the holding portion 403, to prevent the piston 300 from extending out of the bore 210 beyond a predetermined length. This has the effect of facilitating the assembling or disassembling of the piston 300 into or from the modulator block 200.

The function and operation of other elements shown in FIG. 5 are the same as those of the above described fifth embodiment of the present invention shown in FIG. 4.

Eighth Embodiment

Although a pump for a brake system consistent with an eighth embodiment of the present invention is not shown in the drawing, it is noted that the present embodiment is similar to the above described seventh embodiment except for the fact that the guide member 401 and sealing member 402 of the fixing unit 400 are integrally formed with each other.

Specifically, in the eighth embodiment of the present invention, the guide member 401 and sealing member 402 are made of the same elastic material as each other to form the single fixing unit 400, so as to perform both piston guiding and sealing functions together.

As apparent from the above description, the present invention provides a pump for a brake system having the following several effects. Firstly, the pump can safely and efficiently guide reciprocating motions of a piston, and achieve an increase in sealing performance in accordance with the compression of oil in a bore. Further, the pump can enhance durability thereof by reducing wear between the piston and the bore, and facilitate the assembling or disassembling of the piston, etc. into or from a modulator block.

Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. 

1. A pump for a brake system comprising: a bore formed in a modulator block and connected to a suction port and discharge port; a piston installed in the bore to perform rectilinear reciprocating motions, the piston comprising an oil flow path to move an oil suctioned through the suction port toward the discharge port; an inlet valve to open and close the oil flow path in accordance with the motions of the piston and an outlet valve to selectively allow the discharge of the compressed oil; and a fixing unit comprising a guide member provided around the piston to be coupled to the bore and adapted to guide the motions of the piston and a sealing member provided around the piston to be coupled to the bore and adapted to keep between the bore and the piston in an air-tightness state.
 2. The pump according to claim 1, wherein the guide member and sealing member are integrally formed with each other to constitute the fixing unit.
 3. The pump according to claim 1, wherein the piston has a protruding portion to be caught by the fixing unit, so as to prevent the piston from extending out of the bore beyond a predetermined length.
 4. The pump according to claim 1, wherein the inlet valve comprises a valve seat formed at an end of the oil flow path, a valve opening/closing member to open and close the valve seat, a valve spring to elastically support the valve opening/closing member, and a holder to hold the valve spring at a fixed position, the holder having an end configured to be caught by the fixing unit, so as to prevent the piston from extending out of the bore beyond a predetermined length.
 5. The pump according to claim 1, further comprising: a guide bush provided between the piston and the bore to guide the motions of the piston; and a sliding seal member adapted to slide between the guide bush and the fixing unit, so as to keep between the piston and the bore in an air-tightness state, wherein the fixing unit is extended from the inlet valve of the piston and adapted to support the sliding seal member to thereby prevent the sliding seal member from sliding beyond a predetermined distance.
 6. The pump according to claim 1, further comprising: a valve seat coupled to the piston, the valve seat defining an exit of the oil flow path to be opened and closed by the inlet valve, wherein the valve seat has a protruding portion to be caught by the fixing unit, so as to prevent the piston from extending out of the bore beyond a predetermined length.
 7. The pump according to claim 1, wherein the piston has a stepped portion defined between different outer-diameter portions thereof, and the fixing unit has a holding portion defined between different inner-diameter portions thereof, the stepped portion being caught by the holding portion to prevent the piston from extending out of the bore beyond a predetermined length. 